Attempts to count a nation's assets date back to the Bible. But the Enlightenment saw the first efforts to do so in a precise way.

China is in an economic swoon at the moment, if you believe some recent readings suggesting that industrial activity is slowing. Investors in Japan were spooked last month by a record trade deficit in 2013. Closer to home, economists debate quarterly GDP numbers in the U.S. to determine how the current recovery compares with those in the past.

In these and countless other ways, economic data shape our political debates, our business decisions and our investment choices. Yet, as Zachary Karabell points out in "The...